Based on what is rendered in Crysis the performance is totally justified and I've played it at 1080p with almost all veryhigh settings (custom config, with "high" shadows, and regular motionblur, DoF). You want higher settings/framerate then you need to get SLI/CF because that is the true high-end solution not just a single high-end card.

Edit: Slawter just told me that the Uncharted demo was 720p and I highly doubt the retail version magically runs at 1080p "natively", it's just upscaled from 720p to 1080p.